The invention concerns a forked thill head attachment for adjustably mounting a forked thill to a mast of a rigging.
Known from DE-OS No. 33 15 987 is a mast/forked thill connection, for a rigging for a surfboard which, according to FIG. 14, comprises a guide disposed in a recess in the forked thill head. On the lagging end of the guide are installed two clamping jaws on appropriate add-on members. The add-on members are slightly conically tapered toward the front and are firmly pressed into a corresponding recess in the forked thill head by a screw element located at the front end in the forked thill head. The screw element acts upon the flexible suspension in the direction for shortening in order to achieve the clamping effect.
However, this arrangement has several disadvantages. For one thing, a firm attachment and gripping about a mast cannot be achieved through such a flexible suspension. Moreover, manufacturing difficulties arise from the relatively complicated recess into which the flexible suspension must be brought. Besides this, since the clamping jaws are supported only on the add-on members on the forked thill head, a firm gripping about a mast is not guaranteed. Above all, even if mast thicknesses vary only slightly, the clamping jaws may not grip the mast firmly enough, because they already lie against one another at their parting line. On the other hand, if the mast is thicker, the add-on members supporting the clamping jaws cannot be pressed completely into the corresponding recess on the forked thill head, so that there exists only point or line contact between the members and the rim of the recess on the inside part of the forked thill head. This results in only a relatively loose and unsteady connection.
Known also from U.S. Pat. No. 4,516,873 is a forked thill-mast connection comprising two clamping jaws encircled by the forked thill head. Here, by pivoting of the forked thill head, the clamping jaws gripping about the mast will be able to support themselves.
However, the disadvantage - if the mast is thinner - is that no firm encirclement is realized. If a somewhat thicker mast is used, this can lead to non-functionability of the arrangement since, the forked thill cannot be swung into its horizontal position of usage, because the two clamping jaws cannot be pressed together into the required compressed end-position.
Moreover, in the first reference treated, tilting of the forked thill and firm locking of the mast cannot be accomplished simultaneously. Actually, in the second reference treated this is possible, but with the disadvantage that a firm support of the clamping jaw, gripping about the mast on the inner side of the forked thill head, is no longer certain.
Forked thill head attachments are also known from DE-OS Nos. 28 46 017 and 28 21 263. In these arrangements, the forked thill head is bendable at least slightly at its forward end, or subsequently swingable or movable, whereby a fixing arrangement running transversely between both halves of the forked thill head is said to enable a firm attachment to the mast. However, a firm connection here is possible only with a tiresome rotation of the attaching mechanism, and, because of the small diameter of an associated knurled nut, the forces to be applied are so great that connection is not practical with the fingers.
Moreover, the threaded rod may turn in a direction to be loosened during surfing. In the case of this last mentioned reference, there is shown no appropriate adjustment.